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ST16C650A
2.90V TO 5.5V UART WITH 32-BYTE FIFO
REV. 5.0.0
FCR[2]: TX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’.
• Logic 0 = No transmit FIFO reset (default).
• Logic 1 = Reset the transmit FIFO pointers and FIFO level counter logic (the transmit shift register is not
cleared or altered). This bit will return to a logic 0 after resetting the FIFO.
FCR[3]: DMA Mode Select
Controls the behavior of the TXRDY# and RXRDY# pins. See “DMA Mode” on page 11.
• Logic 0 = DMA Mode disabled (default).
• Logic 1 = DMA Mode enabled.
FCR[5:4]: Transmit FIFO Trigger Select
(logic 0 = default, TX trigger level = one)
These 2 bits set the trigger level for the transmit FIFO interrupt. The UART will issue a transmit interrupt when
the number of characters in the FIFO falls below the selected trigger level, or when it gets empty in case that
the FIFO did not get filled over the trigger level on last re-load. Table 10 below shows the selections. EFR bit-4
must be set to ‘1’ before these bits can be accessed.
FCR[7:6]: Receive FIFO Trigger Select
(logic 0 = default, RX trigger level =1).
The FCTR Bits 6-7 are associated with these 2 bits. These 2 bits are used to set the trigger level for the
receiver FIFO interrupt. Table 10 shows the complete selections..
TABLE 10: TRANSMIT AND RECEIVE FIFO TRIGGER LEVEL SELECTION WITH AUTO RTS HYSTERESIS
TRANSMIT INT RECEIVE INT
AUTO RTS
DE-ASSERT
AUTO RTS
RE-ASSERT
FCR
BIT-7
FCR
BIT-6
FCR
BIT-5
FCR
BIT-4
TRIGGER
LEVEL
TRIGGER
LEVEL
COMPATIBILITY
0
0
1
1
0
1
0
1
16
8
16C650A compati-
ble.
24
30
0
0
1
1
0
1
0
1
8
16
24
28
28
0
8
16
24
28
16
24
4.6
Line Control Register (LCR) - Read/Write
The Line Control Register is used to specify the asynchronous data communication format. The word or
character length, the number of stop bits, and the parity are selected by writing the appropriate bits in this
register.
LCR[1:0]: TX and RX Word Length Select
These two bits specify the word length to be transmitted or received.
BIT-1
BIT-0
WORD LENGTH
0
0
1
1
0
1
0
1
5 (default)
6
7
8
29
EXAR [ EXAR CORPORATION ]
